Copolymers of perfluorobutadiene and vinyl alkyl ethers and method of preparation thereof



.in the alkyl group.

COPOLYMERS F PERFLUOROBUTADIENE AND VINYL ALKYL ETHERS AN D METHOD OFPREP- ARATION THEREOF John M. Hoyt, Woodside, 'N. Y., assignor, by mesneassignments, to Minnesota Mining and Manufacturing Company, St. Paul,Minn, .a corporation of Delaware No Drawing. Application January 13,1955 Serial No..481,690

12 Claims. (Cl. 260-875) This invention relates to novel copolymersofxperfluorobutadiene with vinyl alkyl ethers.

The polymerization of perfluorobutadiene at autogenous pressures in thepresence of conventional radicalforming promoters leads to theproduction of polyperfiuorobutadienes having molecular weights in theoil andgrease range. The use of extreme pressures (16,000 kg./cm. isrequired to produce high polymers having useful mechanical properties.Vinyl ethers also fail to form high molecular weight polymers in thepresence of radicalforming promoters. It has now been found, however,that perfluorobutadiene and vinyl ethers readily copolymerize in thepresence of radical-forming promoters to form high molecular weightcopolymers which are plastic or rubbery in character.

In accordance with the present invention, copolymers ofperfluorobutadiene and vinyl alkyl ethers are produced by copolymerizingthe monomers to produce copolymers which are of value as protectivecoatings on metal; and fabric surfaces, in producing films andadhesives, and as substitutes for natural rubber. The copolymers.exhibit to a significant degree the properties associated-with thefluoroand fluorochloro-carbon plastics such as high thermal and chemicalresistance, but possess, in addition, other desirable properties such asimprovedsolubility, workability, and processability in comparison to thefluoroand fiuorochlorocarbon plastics. Marked adhesion of thesecopolymers to metal surfaces has been noted and it is believed thisproperty is a result of the presence of the ether oxygen in thecopolymer.

The vinyl alkyl ethers which may be copolymerized withperfluorobutadiene to produce the. copolymers of the invention are thosehaving from 1 to 8 carbon atoms Exemplary of suchcompounds are vinylmethyl ether, vinyl ethyl ether, vinyl n-propylether, vinyl isopropylether, vinyl n-butyl ether, vinyl .isobutyl ether, vinyl t-butyl ether,vinyl 2-ethylhexyl ether, vinyl 2-chloroethyl ether, vinyl1,l,2,2-tetrafiuoroetl1yl ,ether and vinyl 1,1,Z-trifluoro-Z-chloroethylether. ,In addition to halogen, the alkyl group may be substituted withalkoxy groups, as in vinyl Z-methoxyethyl etherand vinyl 2-butoxy ethylether.

The copolymers of the invention maybe prepared in various comonomerratios using any of the conventional alkaline emulsion or masspolymerization recipes. Since acid media tend to promote the hydrolysisof the vinyl ethers, acid emulsion and suspension systems are notsuitable for use in the copolymerization reactions of .the invention.The pH of the system should beno lower than 6, and preferably is 7 orabove. The temperature employed in the copolymerization reaction may bebetween about 30 C. and 150 C. Where an aqueous "system is used, thetemperature will'be in-the range of about 0 C. to 100 C. I

For example, an emulsion catalyst system, containing water, soap, and aperoxy compound, may be used. The different types of emulsion systemsmay be conveniently differentiated on the basis of the catalyst systememweight per parts of total comonomers present. emulsion polymerizationis conducted under alkaline con- 2,834,766 Patented May 13, 1958 ployedto initiate the polymerization. One type is that in which thepolymerization is initiated by employing a 'redox catalyst system,comprisingbetween about 0.01

-to about 1 part by weight per 100 partsof total comonomers present, ofan organic oxidant and an activator droperoxide, diisopropylbenzenehydroperoxide, triisoprylbenzene hydroperoxide, methylcyclohexanehydroperoxide, tertiary-butyl perbenzoate, and tertiarybutylhydroperoxide. A typical activator solution may consist of about 0.01 to1.0 part by weight per 100 parts of total comonomers present, of avariable valence metal salt, for example ferrous sulfate, about 0.1 to10.0 parts by weight of sodium pyrophosphate, and about 0.1 to 10.0parts by weight of a reducing sugar, such as dextrose, fructose, orlevulose. I

Another type ofemulsion catalystsystem is that which comprises about0.05 to 5 parts by weight per 100 parts of total comonomers present of apersulfate as the oxidant,'and which preferably comprises between about0.1 and about 0.5 part by weight of an inorganic persulfate, such aspotassium persulfate, sodium persulfate, or am- I monium persulfate.

.erably a metal salt, such as the potassium or sodium salt, derived fromsaturated aliphatic acids, the optimum chain length of the acidbeing'between about 14 and about 20 carbon atoms, or.from:polyfiuorocarboxylic acids or perfluorochlorocarboxylic acids. Thepolyfluorocarboxylic acid salts which may be used are those disclosed inU. S. Patent No. 2,559,752, and the nonacidic derivatives. of theacidsdisclosed therein as being eflicacious dispersing agents inpolymerization reactions may also be used in the process of the presentinvention. The perfluorochlorocarboxylic acid salts which may be used inthe process of the present invention are those disclosed in copendingapplication Serial No.. 463,073, filed October 18, 1954, as being usefulas dispersing agents in polymerization reactions. The soap is generallypresent in a quantity between about 0.5 and about 10 parts by Theditions, and the pH should be maintained between about 9 and 11 in orderto prevent gelling of the soap. The pH may be adjusted, if desired, bythe addition of suitable buffers.

As indicated above, the copolymerization reaction also may be carriedout under the aforementioned temperature conditions, with a temperaturebetween about -20 C. and 60 C. being preferred, in a mass or bulkpolymerization system employing an organic peroxide promoter. Of thesepromoters, substituted acetyl peroxides are preferably used in carryingout the copolymerization in the temperature range from about 30 C. toabout 30 C. Trichloroacetyl peroxide is the preferred promoter of thistype. Other halogen-substituted organic peroxides which are suitable forcarrying out the copolymerization in a mass copolymerization system inthe temperature range from about 30 C. to about 30 C. aretrifluoroacetyl peroxide, difiuoroacetyl peroxide, 2,4-di chlorobenzoylperoxide, chloroacetyl peroxide, and perfluoropropionyl peroxide. In thetemperature range from about 30 C. to C., the copolymerization reactionmay be carried out in a mass or bulk copolymerization system employingorganic peroxides such as acetyl peroxide, benzoyl peroxide, lauroylperoxide, or t-butylpen oxide; in the upper portion of this temperaturerange, t-butyl peroxide is preferred.

The copolymers of this invention may be prepared at .autogenouspressures, i. e., atpressures no higher than about 700 pounds per squareinch. The reaction time may be between about 0.1 hour and 100 hours,preferably about to 75 hours.

Polymerization modifiers may also be employed to reduce the molecularweight of the copolymer products and thereby increase the solubility andease of processing thereof. Exemplary of such modifiers are chloroform,carbon tetrachloride, trichloroacetyl chloride, brornotrichloromethane,and dodecyl mercaptan. These modifiers are generally added in quantitiesbetween about 0.1 to parts by weight per 100 parts of total comonomerscharged. Chloroform is the preferred modifier.

The invention will be further illustrated by reference to the followingspecific examples in which all parts are by weight:

EXAMPLE 1 Copolymer of perfluorobutadiene and vinyl 2-chl0r0ethyl etherThe following alkaline emulsion polymerization catalyst system wasemployed in carrying out the polymerization reaction:

Parts by weight After flushing a heavy walled glass polymerization tubewith nitrogen, the tube was charged with 180 parts of a bufferedpotassium fatty acid soap solution having a pH of 10 and which wasobtained by dissolving 5.0 parts of soap in 160 parts of deionizedwater, adjusting the pH to 10.0 with a 5 percent solution of potassiumhydroxide followed by the addition of parts of a concentrated standardbuffer solution having a pH value of 10.0. The polymerization tube wasthen placed in a solid carbon dioxide-acetone bath. When the contents ofthe tube were frozen solid, 20 parts of an aqueous solution containing0.3 part of potassium persulfate were added, and the contents of thetube were refrozen. There were then added 39.6 parts of freshlydistilled and purified vinyl 2-chloroethyl ether and, after the contentsof the tube were refrozen, the tube was evacuated while connected to agas transfer system. Thereafter, 60.4 parts of perfluorobutadiene wereflash distilled into the tube to make up a total monomer chargecontaining 50 mole percent of each monomer. The tube was closed androtated end-over-end in a water bath set at a temperature of 50 C. for aperiod of 5 hours under autogenous pressure. The contents of the tubewere then frozen in a solid carbon dioxide-trichloroethylene bath tocoagulate the polymer product. Excess vinyl Z-chloroethyl ether wasremoved with steam. The coagulated polymer product was collected anddried in vacuo at a temperature of 35 C. The product was a rubber,obtained in a 50 7 percent conversion of total monomers charged.Analysis for chlorine and fluorine content showed the product to contain14 mole percent of combined perfiuorobutadiene and 86 mole percent ofcombined vinyl 2-chloroethyl ether.

A flexible and clear film was obtained by pressing this copolymer for 30seconds at 300 F. at a pressure of 5000 p. s. i. between steel platescovered with aluminum foil.

EXAMPLE 2 Copolymer of perfluoro-butadiene and vinyl ethyl ether Apolymerization tube was charged with the same bufiered soap andpotassium persulfate solution and in the same manner set forth inExample 1 above. Thereafter, the tube was charged with 30.8 parts offreshly distilled vinyl ethyl ether and 69.2 parts ofperfluorobutadiene, corresponding to a total monomer charge containing50 mole percent of each monomer. The polymerization was conducted for 22hours under autogenous pressure at a temperature of 50 C., and theproduct was worked-up following the general procedure of Example 1above. A solid product was obtained in an 89 percent conversion, basedupon the total monomers charged. Analysis for fluorine content showedthis product to contain 47 mole percent of combined perfluorobutadieneand 53 mole percent of combined vinyl ethyl ether.

EXAMPLE 3 Copolymer of perfluorobutadiene and vinyl isobutyl ether Thesame general recipe of Example 1 above was employed except that 4.5parts of soap and 16.4 parts of the standard buffer solution were usedinstead of 5.0 parts and 20.0 parts, respectively. After charging aglass polymerization tube with the buttered soap and potassiumpersulfate solutions as described in Example 1 above, the tube wasfurther charged with 36.2 parts of vinyl isobutyl ether and 63.8 partsof perfluorobutadiene, corresponding to a total monomer chargecontaining 50 mole percent of each monomer. The polymerization wasconducted for 18 hours under autogenous pressure at a temperature of 50C., and the product was worked-up following the general procedure ofExample 1 above. A short rubber was obtained in a 96 percent conversion,based upon the total monomers charged. Analysis for fluorine contentshowed the product to contain 52 mole percent of combinedperfluorobutadiene and 48 mole percent of combined vinyl isobutyl ether.

A clear film was obtained by pressing this copolymer for 30 seconds at300 F. at a pressure of 8000 p. s. i. between steel plates covered withaluminum foil. The film strongly adhered to the aluminum foil.

EXAMPLE 4 Copolymer of perfluorobutadiene and vinyl methyl ether Usingthe same catalyst system and following the same general procedure ofExample 1 above, a heavy walled glass polymerization tube is chargedwith 26.3 parts of vinyl methyl ether and 73.7 parts ofperfluorobutadiene corresponding to a total monomer charge containing 50mole percent of each monomer. The polymerization is conducted for aperiod of 18 hours under autogenous con ditions of pressure at atemperature of 50 C. A solid copolymeric product is obtained.

EXAMPLE 5 Copolymer of perfluorobutadiene and vinyl 1,1,2-triflu0r0-Z-chloroethyl ether Using the same polymerization catalyst system andfol lowing the same general procedure of Example 1 above, a glasspolymerization tube is charged with 49.8 parts of vinyl1,1,2-trifluoro-2-chloroethyl ether and 50.2 parts of perfluorobutadienecorresponding to a total monomer charge containing 50 mole percent ofeach monomer. The polymerization is conducted for a period of 17 hoursunder autogenous conditions of pressure at a temperature of 50 C. Asolid copolymeric product is obtained.

It will be obvious to those skilled in the art that many inventionwithout departing from the spirit thereof, and the invention includesall such modifications.

I claim: 7

1. A copolymer of a vinyl alkyl ether having 1 to 8 carbon atoms in thealkyl group and in which said alkyl group is selected from the groupconsisting of an unsub stituted alkyl radical, a haloalkyl radical andan alkoxy substituted alkyl radical, and perfluorobutadiene.

2. A copolymer of vinyl 2-chloroethyl ether and perfluorobutadiene.

3. A copolymer of vinyl ethyl ether and perfluoro butadiene.-

4. A copolymer of vinyl isobutyl ether and perfluorobutadiene.

5. A copolymer of vinyl methyl ether and perfiuorobutadiene. r

6. A copolymer of vinyl l,1,2-trifluoro-2-chloroethyl ether andperfluoro'outadiene.

7. A process which comprises copolymerizing a vinyl alkyl ether having 1to 8 carbon atoms in the alkyl group and in which said alkyl group isselected from the group consisting of an unsubstituted alkyl radical, ahaloalkyl radical and an alkoxy substituted alkyl radical, withperfluorobutadiene at a temperature between about -30 C. and about 150C.

8. A process which comprises copolymerizing vinyl 2-chloroethy1 etherand perfluorobutadiene at a temperature between about -30 C. and about150 C.

9. A process which comprises copolymerizing vinyl ethyl ether andperfiuorobutadiene at a temperature between about 30 C. and about 150 C.

10. A process which comprises copolymerizing vinyl isobutyl ether andperfluorobutadiene at a temperature between -30 C. and about 150 C.

1,1,2-trifluoro-2-chloroethyl ether and perfiuorobutadiene at atemperature between about 30 C. and about References Cited in the fileof this patent UNITED STATES PATENTS 2,066,330 Carothers et al Jan. 5,1937 2,600,802 Passino June 17, 1952 2,631,997 Stewart Mar. 17, 19532,647,110 Wiseman July 28, 1953 2,705,706 Dittrnan et al Apr. 5, 19552,710,854 Seelig June 14, 1955 2,742,454 Rearick et a1 Apr. '17, 19562,750,431 Tarrant et a1 June 12, 1956

1. A COPOLYMER OF A VINYL ALKYL ETHER HAVING 1 TO 8 CARBON ATOMS IN THEALKYL GROUP AND IN WHICH SAID ALKYL GROUP IS SELECTED FROM THE GROUPCONSISTING OF AN UNSUBSTITUTED ALKYL RADICAL, A HALOALKYL RADICAL AND ANALKOXY SUBSTITUTED ALKYL RADICAL, AND APERFLUOROBUTADIENE.
 7. A PROCESSWHICH COMPRISES COPOLYMERIZING A VINYL ALKYL ETHER HAVING 1 TO 8 CARBONATOMS IN THE ALKYL GROUP AND IN WHICH SAID ALKYL GROUP IS SELECTED FROMTHE GROUP CONSISTING OF AN UNSUBSTITUTED ALKYL RADICAL, A HALOALKYLRADICAL AND AN ALKOXY SUBSTITUTED ALKYL RADICAL, WITH PERFLUOROBUTADIENEAT A TEMPERATURE BETWEEN ABOUT -30*C. AND ABOUT 150*C.